Age and growth determinations in the catfish, Chrysichthys nigrodigitatus (Lacépède) by use of the dorsal spine

Annual rings on the first dorsal spine were used to determine the age and growth of the catfish, Chrysichthys nigrodigitatus (Lacépède), in the Lagos Lagoon, Nigeria. From back-calculations, it was found that the mean total length ofthe species when the first annulus was formed was 18.5 cm, 32.6 cm for second annulus, 43.5 cm for the third annulus and 53.9 cm for the fourth annulus. It was shown that this species in the Lagos Lagoon attained four years of age and that the fastest growth in length was achieved during the first year of life. Thereafter, increase in length gradually decreased with age. The relationship between the body length and dorsal spine radius was shown to be linear and highly correlated.